The New South Wales Government will proceed with the sale of the state's electricity generators and the sale or lease of the Cobbora coal mine development after getting the green light in the form of scoping studies.

NSW Treasurer Mike Baird on Thursday said the sell-off would free up to $3 billion for transport, school and hospital projects across the state.

Mr Baird said the sale process for the generators would begin immediately and continue through to 2014.

The planning and approvals process for the development of Cobbora was also on track, he said.

"The expert advisors put the potential loss to the state currently at about $1.5 billion for the Cobbora transaction," Mr Baird said in a statement.

"The O'Farrell Government is determined to minimise these risks and liabilities and will explore all possible options for the mine development, including investigating whether alternative sources of coal are available to satisfy its obligations under existing coal supply agreements."

NSW Greens MP John Kaye warned the Cobbora project was uneconomic and Mr Baird's plans to sell it off wouldn't protect households from decades of hidden power privatisation costs.

"Privatising power stations will always be a bad deal for the state's economy and environment," he said in a statement.

"But propping up the sale price with below-cost coal contracts will make the impacts much worse."

Mr Kaye said the mine would not be able to proceed without massive government subsidies, jeopardising its plan sell the power stations.

"The O'Farrell government will leave costs, risks and liabilities in public hands to fatten up the coal mine and the power stations for sale," he said.

"Power privatisation will lock NSW into power station greenhouse gas emissions of at least 60 million tonnes a year as well as the on-going costs of Cobbora."